In recent years, e.g., a liquid crystal display device has been widely used for electrical equipment, including a liquid crystal television, a monitor, a portable telephone, a digital camera, and an information terminal, as a flat panel display (display cell) having features such as small thickness and light weight compared to a conventional Braun tube. In the liquid crystal display device, it is known to use an active matrix substrate for a liquid crystal panel (display panel). The active matrix substrate includes the following: a plurality of data lines (source lines) and a plurality of gate lines (scanning lines) that are arranged in a matrix; switching elements such as thin film transistors (TFTs) that are provided in the vicinity of each of the intersections of the data lines and the scanning lines; and pixels that are arranged in a matrix and include pixel electrodes connected to the switching elements.
There is a growing demand for the display cell to have high resolution or small size. In the display cell, many lines are routed to terminals from one side of a matrix region in which the data lines and the scanning lines are arranged in a matrix (i.e., a pixel array in which the pixels are arranged in a matrix). It is desirable that these lines be within a predetermined area. In other words, it is desirable that a portion that surrounds the display cell and does not affect display, which is called a frame, be reduced.
In order to reduce the frame around the display cell, an active matrix substrate includes a scanning signal drive circuit (gate driver) that is monolithically formed on a base material (low-temperature polycrystalline silicon) of the substrate. This configuration can reduce the frame other than the portion located on the terminal side in which the terminals are provided.
On the other hand, lines called video signal lines are connected to the data lines and routed in the frame on the terminal side. However, it is difficult to reduce this frame on the terminal side, since the number of lines is very large compared to the monolithic circuit element. Therefore, in the conventional active matrix substrate, proposals have been made mainly to improve the line width, line pitch, and wiring structure of the video signal lines.
Specifically, in the conventional active matrix substrate, as described in Patent Document 1 or Patent Document 2, the video signal lines are composed of two different conductive layers, i.e., a lower-layer metal film and an upper-layer metal film, so that the video signal lines can be routed at a narrower pitch.
Moreover, in the conventional active matrix substrate, the video signal lines are laid in a line region between the matrix region and a terminal region in which the terminals are arranged, and the line region is defined so that the line pitch becomes narrower in the direction from the matrix region to the terminal region (i.e., the video signal lines are routed to converge in a fan shape). The size of the terminal region is smaller than that of one side of the matrix region. Thus, the FPC or data driver (driver IC) connected to the terminals in the terminal region can be reduced in size. This may result in a reduction in cost of the members such as the FPC and the driver IC.